L1 slide 19: Processes and cycles (ENGR5003)

L1 slide 19: Processes and cyclesFrom lectureCurrent specThird4 marks4 min

A gas in a piston-cylinder is compressed from State 1 to State 2. It is then expanded back to State 1 through a different path.

Formulas you may need

First law, closed system: $Q = \Delta U + W$ (on the formula sheet)
Boundary work: $W = \int p\,dV$ , the area under the p-V curve (on the formula sheet)
Round a cycle: $\oint dU = 0$ , so $\oint \delta Q = \oint \delta W$ (learn this)

(a)
Which statement is correct?
AThe gas has undergone one process.BThe gas has undergone two processes and completed a cycle.CThe gas has undergone two cycles.DThe initial and final states are different.
[1]
(b)
What is the net change in the thermodynamic properties of the gas after one complete cycle?
[1]
(c)
Does that mean $Q = 0$ and $W = 0$ for the cycle? Explain.
[2]